Enhanced photoelectrochemical activity of Nickel-phosphate decorated phosphate-Fe2O3 photoanode for glycerol-based fuel cell

Abstract

The nickel-phosphate decorated phosphate-Fe2O3 photoanode (NiPi/Pi-Fe2O3) was fabricated by coating phosphate modified hematite (Pi-Fe2O3) with naturally abundant nickel-phosphate complexes (NiPi). X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy studies showed that NiPi was uniformly distributed on Pi-Fe2O3 surface as amorphous form. With the decoration of NiPi, the photocurrent of Pi-Fe2O3 was enhanced by ca. 2 times at 1.5V (vs. RHE). The NiPi/Pi-Fe2O3 also exhibited higher maximum power generation in photoelectrochemical (PEC) glycerol-based fuel cell, which was ca. 2.4 times than that of Pi-Fe2O3. Electrochemical impedance spectroscopy analysis revealed the charge transfer resistance at the interface of Pi-Fe2O3/electrolyte was remarkably decreased by NiPi decoration. NiPi was believed to be not only a hole-conductor that promoting the charge separation but also a catalyst for glycerol oxidation through cyclic changes between the lower and the higher oxidation states of Ni, which were the main reasons for the enhanced PEC response and power generation. The intermediates from glycerol were verified using high performance liquid chromatography, indicating the efficient cleavage of C-C bonds in glycerol on NiPi/Pi-Fe2O3. This work demonstrates NiPi/Pi-Fe2O3 has great potential in PEC fuel cells for the generation of electricity from light energy and biomass energy.